| Message ID | 20220519063923.352540-1-frank.heimes@canonical.com |
|---|---|
| Headers | show |
| Series | KVM nesting support leaks too much memory, might result in stalls during cleanup (LP: 1974017) | expand |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Acked-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com> On Thu, May 19 2022, frank.heimes@canonical.com wrote: > BugLink: https://bugs.launchpad.net/bugs/1974017 > > SRU Justification: > > [Impact] > > * If running KVM with nesting support (e.g. 'kvm.nested=1' on the kernel > command line), the shadow page table code will produce too many entries > in the shadow code. > > * The below mentioned upstream fix will prevent the entries from being > piled up, by checking for existing entries at insert time. > > * This measurably reduces the list length and is faster than traversing > the list at shutdown time only. > > [Fix] > > * a06afe8383080c630a7a528b8382fc6bb4925b61 a06afe838308 > "KVM: s390: vsie/gmap: reduce gmap_rmap overhead" > > [Test Plan] > > * A IBM zSystems or LinuxONE LPAR on a z13 or newer is needed. > > * Ubuntu focal, impish or jammy needs to be installed > and the Ubuntu LPAR setup as (1st level) KVM host, > allowing nested virtualization. > > * Now setup one (or more) KVM virtual machines, > with similar Ubuntu releases, > and define one or more of them again as (2nd level) KVM host. > > * Define several KVM virtual machines on this (2nd level) KVM host > in a memory constraint fashion, > so that a lot of memory mapping is caused. > > * Let such a system run for a while under load. > > * Now shutdown one (or more) 2nd level VMs and notice the > time it takes. > > * With the patch in place this time should be considerably > quicker than without. > > * The result is reduced mapping (gmap_rmap) overhead, > less danger of leaking memory > and a better responding system. > > [Where problems could occur] > > * In case wrong entries are freed up this will harm the virtual > memory management and may even lead to crashes. > > * In case the pointer handling is not done properly, > again crashes may occur. > > * But with net just five new lines the patch is pretty short, readable > and the modifications traceable in arch/s390/mm/gmap.c only. > > * The changes are limited to s390/mm only, > hence don't affect other architectures. > > [Other Info] > > * The commit was upstream accepted in v5.18-rc6. > > * Since the planned target kernel for kinetic is 5.19, > the kinetic kernel does not need to be patched. > > * Hence the SRUs are for jammy, impish and focal. > > Christian Borntraeger (1): > KVM: s390: vsie/gmap: reduce gmap_rmap overhead > > arch/s390/mm/gmap.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > -- > 2.25.1 - -- Regards, Marcelo -----BEGIN PGP SIGNATURE----- iQGzBAEBCgAdFiEExJjLjAfVL0XbfEr56e82LoessAkFAmKGTugACgkQ6e82Loes sAmwXAwAiThoWY38mmcxP5exK0Og9KdFn9YP8SyG+fdXNq9clyxjHOBBhPRw5KBo obbp+t788bzQMM1iu+DGBqeQsYhzpbF92lwCtmU5VL7hbjiO6RzFq7+jGxBQDRca mXWhnjPMgOW/YfMg4R2dF2V/OotwrFA28t7PPmiWBRuhtSlN5kTDquSiVFjDaHgP KZnnwfmQlsY37ZrN9R9F17HACePziXrryh/y/2BnElZJmSU+L7Zh4jCLs3QT8kB3 VS2eaNGi5AixHLK3tBmunXH+972Z5VbJbgjs0DqT61ZhGnkeIeEipFY+ziPerOhO b9+oO006l++AJTXEzPGqgd7EtnTf9gB+WT3SnHUc8Vrj/ypR0tWPO4O9/ixp6OjY 23svaE5SxoAVAhbmPvh3O40Oj8vHXppLpv8FjL1mFXb/nCwoB/jN5RKciAQCRI3v Uz9E+3rZHG5o0ZNgrBHwkGpyXZWYwXigfrgXmgcMgfhCHD88Yqem+bi274Ev3gyM 2dAX2dT0 =rBPE -----END PGP SIGNATURE-----
Acked-by: Bartlomiej Zolnierkiewicz <bartlomiej.zolnierkiewicz@canonical.com> On Thu, May 19, 2022 at 8:40 AM <frank.heimes@canonical.com> wrote: > > BugLink: https://bugs.launchpad.net/bugs/1974017 > > SRU Justification: > > [Impact] > > * If running KVM with nesting support (e.g. 'kvm.nested=1' on the kernel > command line), the shadow page table code will produce too many entries > in the shadow code. > > * The below mentioned upstream fix will prevent the entries from being > piled up, by checking for existing entries at insert time. > > * This measurably reduces the list length and is faster than traversing > the list at shutdown time only. > > [Fix] > > * a06afe8383080c630a7a528b8382fc6bb4925b61 a06afe838308 > "KVM: s390: vsie/gmap: reduce gmap_rmap overhead" > > [Test Plan] > > * A IBM zSystems or LinuxONE LPAR on a z13 or newer is needed. > > * Ubuntu focal, impish or jammy needs to be installed > and the Ubuntu LPAR setup as (1st level) KVM host, > allowing nested virtualization. > > * Now setup one (or more) KVM virtual machines, > with similar Ubuntu releases, > and define one or more of them again as (2nd level) KVM host. > > * Define several KVM virtual machines on this (2nd level) KVM host > in a memory constraint fashion, > so that a lot of memory mapping is caused. > > * Let such a system run for a while under load. > > * Now shutdown one (or more) 2nd level VMs and notice the > time it takes. > > * With the patch in place this time should be considerably > quicker than without. > > * The result is reduced mapping (gmap_rmap) overhead, > less danger of leaking memory > and a better responding system. > > [Where problems could occur] > > * In case wrong entries are freed up this will harm the virtual > memory management and may even lead to crashes. > > * In case the pointer handling is not done properly, > again crashes may occur. > > * But with net just five new lines the patch is pretty short, readable > and the modifications traceable in arch/s390/mm/gmap.c only. > > * The changes are limited to s390/mm only, > hence don't affect other architectures. > > [Other Info] > > * The commit was upstream accepted in v5.18-rc6. > > * Since the planned target kernel for kinetic is 5.19, > the kinetic kernel does not need to be patched. > > * Hence the SRUs are for jammy, impish and focal. > > Christian Borntraeger (1): > KVM: s390: vsie/gmap: reduce gmap_rmap overhead > > arch/s390/mm/gmap.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > -- > 2.25.1
On 19.05.22 08:39, frank.heimes@canonical.com wrote: > BugLink: https://bugs.launchpad.net/bugs/1974017 > > SRU Justification: > > [Impact] > > * If running KVM with nesting support (e.g. 'kvm.nested=1' on the kernel > command line), the shadow page table code will produce too many entries > in the shadow code. > > * The below mentioned upstream fix will prevent the entries from being > piled up, by checking for existing entries at insert time. > > * This measurably reduces the list length and is faster than traversing > the list at shutdown time only. > > [Fix] > > * a06afe8383080c630a7a528b8382fc6bb4925b61 a06afe838308 > "KVM: s390: vsie/gmap: reduce gmap_rmap overhead" > > [Test Plan] > > * A IBM zSystems or LinuxONE LPAR on a z13 or newer is needed. > > * Ubuntu focal, impish or jammy needs to be installed > and the Ubuntu LPAR setup as (1st level) KVM host, > allowing nested virtualization. > > * Now setup one (or more) KVM virtual machines, > with similar Ubuntu releases, > and define one or more of them again as (2nd level) KVM host. > > * Define several KVM virtual machines on this (2nd level) KVM host > in a memory constraint fashion, > so that a lot of memory mapping is caused. > > * Let such a system run for a while under load. > > * Now shutdown one (or more) 2nd level VMs and notice the > time it takes. > > * With the patch in place this time should be considerably > quicker than without. > > * The result is reduced mapping (gmap_rmap) overhead, > less danger of leaking memory > and a better responding system. > > [Where problems could occur] > > * In case wrong entries are freed up this will harm the virtual > memory management and may even lead to crashes. > > * In case the pointer handling is not done properly, > again crashes may occur. > > * But with net just five new lines the patch is pretty short, readable > and the modifications traceable in arch/s390/mm/gmap.c only. > > * The changes are limited to s390/mm only, > hence don't affect other architectures. > > [Other Info] > > * The commit was upstream accepted in v5.18-rc6. > > * Since the planned target kernel for kinetic is 5.19, > the kinetic kernel does not need to be patched. > > * Hence the SRUs are for jammy, impish and focal. > > Christian Borntraeger (1): > KVM: s390: vsie/gmap: reduce gmap_rmap overhead > > arch/s390/mm/gmap.c | 7 +++++++ > 1 file changed, 7 insertions(+) > Applied to focal/impish/jammy:linux. Thanks, Kleber