| Message ID | 20240906160926.750390-2-john.cabaj@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | Revert fix for "Kernel fails to enable XSAVE when running in a “v5” AMD SEV-SNP VM" | expand |
On 06-09-2024 18:09, John Cabaj wrote: > BugLink: https://bugs.launchpad.net/bugs/2079841 > > This reverts commit 8ce273422c040ec77c8bfa58c7d7dbbb570710d0. In oracular:linux-azure it should be 29fa1211e69aa9a21be5517e795b99156a4df78e > > Signed-off-by: John Cabaj <john.cabaj@canonical.com> > --- > arch/x86/kernel/cpu/mshyperv.c | 21 --------------------- > 1 file changed, 21 deletions(-) > > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c > index c9dee20fa8a9..82a356fbde4e 100644 > --- a/arch/x86/kernel/cpu/mshyperv.c > +++ b/arch/x86/kernel/cpu/mshyperv.c > @@ -581,27 +581,6 @@ static void __init ms_hyperv_init_platform(void) > if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) > mark_tsc_unstable("running on Hyper-V"); > > - /* > - * Mask CET Shadow Stack on SEV-SNP due to a CPUID emulation bug in > - * the paravisor on old Azure SEV-SNP hosts, e.g., 10.0.20348.2867-2-0. > - * Due to the bug, paranoid_xstate_size_valid() in a v6.6 or newer > - * kernel prints a warning "XSAVE consistency problem: size 848 != kernel_size 832" > - * and the kernel disables XSAVE completely; the early 'init' program or > - * any later program may get core-dumped due to "invalid opcode", if > - * they assume XSAVE is available (e.g., it looks like > - * libgnutls.so.30.27.0 tries to unconditionally use XSAVE. > - * > - * Note: the SNP paravisor bug only affects a v6.6+ Linux kernel > - * (CET Shadow Stack is firstly enabled in v6.6) when the VM is a "v5" > - * SNP VM on Azure. A "v6" SNP VM is not affected, and a TDX VM is also > - * not affectd since the versions of paravisor for them are already > - * fixed. The fix for the "v5" VMs would roll out around September or > - * October, 2024. > - */ > - if (ms_hyperv.paravisor_present && > - hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) > - setup_clear_cpu_cap(X86_FEATURE_SHSTK); > - > hardlockup_detector_disable(); > } >
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index c9dee20fa8a9..82a356fbde4e 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -581,27 +581,6 @@ static void __init ms_hyperv_init_platform(void) if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) mark_tsc_unstable("running on Hyper-V"); - /* - * Mask CET Shadow Stack on SEV-SNP due to a CPUID emulation bug in - * the paravisor on old Azure SEV-SNP hosts, e.g., 10.0.20348.2867-2-0. - * Due to the bug, paranoid_xstate_size_valid() in a v6.6 or newer - * kernel prints a warning "XSAVE consistency problem: size 848 != kernel_size 832" - * and the kernel disables XSAVE completely; the early 'init' program or - * any later program may get core-dumped due to "invalid opcode", if - * they assume XSAVE is available (e.g., it looks like - * libgnutls.so.30.27.0 tries to unconditionally use XSAVE. - * - * Note: the SNP paravisor bug only affects a v6.6+ Linux kernel - * (CET Shadow Stack is firstly enabled in v6.6) when the VM is a "v5" - * SNP VM on Azure. A "v6" SNP VM is not affected, and a TDX VM is also - * not affectd since the versions of paravisor for them are already - * fixed. The fix for the "v5" VMs would roll out around September or - * October, 2024. - */ - if (ms_hyperv.paravisor_present && - hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) - setup_clear_cpu_cap(X86_FEATURE_SHSTK); - hardlockup_detector_disable(); }
BugLink: https://bugs.launchpad.net/bugs/2079841 This reverts commit 8ce273422c040ec77c8bfa58c7d7dbbb570710d0. Signed-off-by: John Cabaj <john.cabaj@canonical.com> --- arch/x86/kernel/cpu/mshyperv.c | 21 --------------------- 1 file changed, 21 deletions(-)