| Message ID | 20240730123559.35115-1-n.novikov@syntacore.com |
|---|---|
| State | New |
| Headers | show |
| Series | hw/char/riscv_htif: Fix 64-bit var write order in 32-bit system | expand |
On Wed, Jul 31, 2024 at 12:51 AM Nikita Novikov <n.novikov@syntacore.com> wrote: > > When we are trying to write 64-bit value in 32-bit system, the value in HTIF device divides > on 2 separate 32-bit parts. So device expects write to xHOST_OFFSET1 first, then to xHOST_OFFSET2. > But some compilers (ex. CLANG) can change the writing queue (xHOST_OFFSET2 first, xHOST_OFFSET1 second) > because of machine instructions order swapping. That causes wrong behaviour of HTIF device. I don't follow, isn't this MMIO why is the compiler swapping the order? > This patch is removing dependency of writing order, so the device will work correctly regardless of compilers. Urgh, the HTIF is undocumented, so there isn't really a way to know if this is right or not. It kind of seems like the QEMU implementation is the best documentation at the moment [1], so I'm reluctant to make this change. > > Signed-off-by: Nikita Novikov <n.novikov@syntacore.com> > --- > hw/char/riscv_htif.c | 43 +++++++++++++++++++----------------- > include/hw/char/riscv_htif.h | 11 +++++++-- > 2 files changed, 32 insertions(+), 22 deletions(-) > > diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c > index 9bef60def1..d914f158ea 100644 > --- a/hw/char/riscv_htif.c > +++ b/hw/char/riscv_htif.c > @@ -233,7 +233,8 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) > if (cmd == HTIF_CONSOLE_CMD_GETC) { > /* this should be a queue, but not yet implemented as such */ > s->pending_read = val_written; > - s->tohost = 0; /* clear to indicate we read */ > + s->tohost = 0; > + s->tohost_status = 0x0; /* clear to indicate we read */ This seems like a separate change? > return; > } else if (cmd == HTIF_CONSOLE_CMD_PUTC) { > uint8_t ch = (uint8_t)payload; > @@ -258,7 +259,8 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) > * } > */ > s->fromhost = (val_written >> 48 << 48) | (resp << 16 >> 16); > - s->tohost = 0; /* clear to indicate we read */ > + s->tohost = 0; > + s->tohost_status = 0x0; /* clear to indicate we read */ > } > > #define TOHOST_OFFSET1 (s->tohost_offset) > @@ -291,32 +293,33 @@ static void htif_mm_write(void *opaque, hwaddr addr, > { > HTIFState *s = opaque; > if (addr == TOHOST_OFFSET1) { > - if (s->tohost == 0x0) { > - s->allow_tohost = 1; > - s->tohost = value & 0xFFFFFFFF; > - } else { > - s->allow_tohost = 0; > - } > + s->tohost = deposit64(s->tohost, 0, 32, value); > + s->tohost_status |= 0x1; > } else if (addr == TOHOST_OFFSET2) { > - if (s->allow_tohost) { > - s->tohost |= value << 32; > - htif_handle_tohost_write(s, s->tohost); > - } > + s->tohost = deposit64(s->tohost, 32, 32, value); > + s->tohost_status |= 0x2; Won't this break existing users? > } else if (addr == FROMHOST_OFFSET1) { > - s->fromhost_inprogress = 1; > - s->fromhost = value & 0xFFFFFFFF; > + s->fromhost = deposit64(s->fromhost, 0, 32, value); > + s->fromhost_status |= 0x1; > } else if (addr == FROMHOST_OFFSET2) { > - s->fromhost |= value << 32; > - s->fromhost_inprogress = 0; > + s->fromhost = deposit64(s->fromhost, 32, 32, value); > + s->fromhost_status |= 0x2; > } else { > - qemu_log("Invalid htif write: address %016" PRIx64 "\n", > - (uint64_t)addr); > + qemu_log("Invalid htif write: address %016" HWADDR_PRIu "\n", addr); > + } > + if (s->tohost_status == 0x3) { > + htif_handle_tohost_write(s, s->tohost); > + s->tohost_status = 0x0; > } > } 1: https://github.com/riscv-software-src/opensbi/issues/238 Alistair > > static const MemoryRegionOps htif_mm_ops = { > .read = htif_mm_read, > .write = htif_mm_write, > + .valid.min_access_size = 4, > + .valid.max_access_size = 8, > + .impl.min_access_size = 4, > + .impl.max_access_size = 4 > }; > > HTIFState *htif_mm_init(MemoryRegion *address_space, Chardev *chr, > @@ -343,8 +346,8 @@ HTIFState *htif_mm_init(MemoryRegion *address_space, Chardev *chr, > s->tohost_offset = tohost_offset; > s->fromhost_offset = fromhost_offset; > s->pending_read = 0; > - s->allow_tohost = 0; > - s->fromhost_inprogress = 0; > + s->tohost_status = 0; > + s->fromhost_status = 0; > qemu_chr_fe_init(&s->chr, chr, &error_abort); > qemu_chr_fe_set_handlers(&s->chr, htif_can_recv, htif_recv, htif_event, > htif_be_change, s, NULL, true); > diff --git a/include/hw/char/riscv_htif.h b/include/hw/char/riscv_htif.h > index df493fdf6b..2b6d50dc60 100644 > --- a/include/hw/char/riscv_htif.h > +++ b/include/hw/char/riscv_htif.h > @@ -27,8 +27,15 @@ > #define TYPE_HTIF_UART "riscv.htif.uart" > > typedef struct HTIFState { > - int allow_tohost; > - int fromhost_inprogress; > + /* > + * Vars below can be in 4 states: > + * 0x0 - nothing written > + * 0x1 - xHOST_OFFEST1 written > + * 0x2 - xHOST_OFFSET2 written > + * 0x3 - Both written > + */ > + int tohost_status; > + int fromhost_status; > > uint64_t tohost; > uint64_t fromhost; > -- > 2.34.1 > >
diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c index 9bef60def1..d914f158ea 100644 --- a/hw/char/riscv_htif.c +++ b/hw/char/riscv_htif.c @@ -233,7 +233,8 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) if (cmd == HTIF_CONSOLE_CMD_GETC) { /* this should be a queue, but not yet implemented as such */ s->pending_read = val_written; - s->tohost = 0; /* clear to indicate we read */ + s->tohost = 0; + s->tohost_status = 0x0; /* clear to indicate we read */ return; } else if (cmd == HTIF_CONSOLE_CMD_PUTC) { uint8_t ch = (uint8_t)payload; @@ -258,7 +259,8 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) * } */ s->fromhost = (val_written >> 48 << 48) | (resp << 16 >> 16); - s->tohost = 0; /* clear to indicate we read */ + s->tohost = 0; + s->tohost_status = 0x0; /* clear to indicate we read */ } #define TOHOST_OFFSET1 (s->tohost_offset) @@ -291,32 +293,33 @@ static void htif_mm_write(void *opaque, hwaddr addr, { HTIFState *s = opaque; if (addr == TOHOST_OFFSET1) { - if (s->tohost == 0x0) { - s->allow_tohost = 1; - s->tohost = value & 0xFFFFFFFF; - } else { - s->allow_tohost = 0; - } + s->tohost = deposit64(s->tohost, 0, 32, value); + s->tohost_status |= 0x1; } else if (addr == TOHOST_OFFSET2) { - if (s->allow_tohost) { - s->tohost |= value << 32; - htif_handle_tohost_write(s, s->tohost); - } + s->tohost = deposit64(s->tohost, 32, 32, value); + s->tohost_status |= 0x2; } else if (addr == FROMHOST_OFFSET1) { - s->fromhost_inprogress = 1; - s->fromhost = value & 0xFFFFFFFF; + s->fromhost = deposit64(s->fromhost, 0, 32, value); + s->fromhost_status |= 0x1; } else if (addr == FROMHOST_OFFSET2) { - s->fromhost |= value << 32; - s->fromhost_inprogress = 0; + s->fromhost = deposit64(s->fromhost, 32, 32, value); + s->fromhost_status |= 0x2; } else { - qemu_log("Invalid htif write: address %016" PRIx64 "\n", - (uint64_t)addr); + qemu_log("Invalid htif write: address %016" HWADDR_PRIu "\n", addr); + } + if (s->tohost_status == 0x3) { + htif_handle_tohost_write(s, s->tohost); + s->tohost_status = 0x0; } } static const MemoryRegionOps htif_mm_ops = { .read = htif_mm_read, .write = htif_mm_write, + .valid.min_access_size = 4, + .valid.max_access_size = 8, + .impl.min_access_size = 4, + .impl.max_access_size = 4 }; HTIFState *htif_mm_init(MemoryRegion *address_space, Chardev *chr, @@ -343,8 +346,8 @@ HTIFState *htif_mm_init(MemoryRegion *address_space, Chardev *chr, s->tohost_offset = tohost_offset; s->fromhost_offset = fromhost_offset; s->pending_read = 0; - s->allow_tohost = 0; - s->fromhost_inprogress = 0; + s->tohost_status = 0; + s->fromhost_status = 0; qemu_chr_fe_init(&s->chr, chr, &error_abort); qemu_chr_fe_set_handlers(&s->chr, htif_can_recv, htif_recv, htif_event, htif_be_change, s, NULL, true); diff --git a/include/hw/char/riscv_htif.h b/include/hw/char/riscv_htif.h index df493fdf6b..2b6d50dc60 100644 --- a/include/hw/char/riscv_htif.h +++ b/include/hw/char/riscv_htif.h @@ -27,8 +27,15 @@ #define TYPE_HTIF_UART "riscv.htif.uart" typedef struct HTIFState { - int allow_tohost; - int fromhost_inprogress; + /* + * Vars below can be in 4 states: + * 0x0 - nothing written + * 0x1 - xHOST_OFFEST1 written + * 0x2 - xHOST_OFFSET2 written + * 0x3 - Both written + */ + int tohost_status; + int fromhost_status; uint64_t tohost; uint64_t fromhost;
When we are trying to write 64-bit value in 32-bit system, the value in HTIF device divides on 2 separate 32-bit parts. So device expects write to xHOST_OFFSET1 first, then to xHOST_OFFSET2. But some compilers (ex. CLANG) can change the writing queue (xHOST_OFFSET2 first, xHOST_OFFSET1 second) because of machine instructions order swapping. That causes wrong behaviour of HTIF device. This patch is removing dependency of writing order, so the device will work correctly regardless of compilers. Signed-off-by: Nikita Novikov <n.novikov@syntacore.com> --- hw/char/riscv_htif.c | 43 +++++++++++++++++++----------------- include/hw/char/riscv_htif.h | 11 +++++++-- 2 files changed, 32 insertions(+), 22 deletions(-)