| Message ID | 20200902135421.31158-1-jiangshanlai@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] kvm x86/mmu: use KVM_REQ_MMU_SYNC to sync when needed | expand |
Lai Jiangshan <jiangshanlai@gmail.com> writes: > From: Lai Jiangshan <laijs@linux.alibaba.com> > > When kvm_mmu_get_page() gets a page with unsynced children, the spt > pagetable is unsynchronized with the guest pagetable. But the > guest might not issue a "flush" operation on it when the pagetable > entry is changed from zero or other cases. The hypervisor has the > responsibility to synchronize the pagetables. > > The linux kernel behaves as above for many years, But > 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) Nit: checkpatch.pl complains here with ERROR: Please use git commit description style 'commit <12+ chars of sha1> ("<title line>")' - ie: 'commit 8c8560b83390 ("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes")' #118: 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) > inadvertently included a line of code to change it without giving any > reason in the changelog. It is clear that the commit's intention was to > change KVM_REQ_TLB_FLUSH -> KVM_REQ_TLB_FLUSH_CURRENT, so we don't > unneedlesly flush other contexts but one of the hunks changed > nearby KVM_REQ_MMU_SYNC instead. > > The this patch changes it back. > > Link: https://lore.kernel.org/lkml/20200320212833.3507-26-sean.j.christopherson@intel.com/ > Cc: Sean Christopherson <sean.j.christopherson@intel.com> > Cc: Vitaly Kuznetsov <vkuznets@redhat.com> > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > --- > Changed from v1: > update patch description > > arch/x86/kvm/mmu/mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 4e03841f053d..9a93de921f2b 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, > } > > if (sp->unsync_children) > - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); > + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); > > __clear_sp_write_flooding_count(sp); FWIW, Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> but it'd be great to hear from Sean).
On Wed, Sep 02, 2020 at 04:12:55PM +0200, Vitaly Kuznetsov wrote: > Lai Jiangshan <jiangshanlai@gmail.com> writes: > > > From: Lai Jiangshan <laijs@linux.alibaba.com> > > > > When kvm_mmu_get_page() gets a page with unsynced children, the spt > > pagetable is unsynchronized with the guest pagetable. But the > > guest might not issue a "flush" operation on it when the pagetable > > entry is changed from zero or other cases. The hypervisor has the > > responsibility to synchronize the pagetables. > > > > The linux kernel behaves as above for many years, But > > 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) > > Nit: checkpatch.pl complains here with > > ERROR: Please use git commit description style 'commit <12+ chars of > sha1> ("<title line>")' - ie: 'commit 8c8560b83390 ("KVM: x86/mmu: Use > KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes")' > #118: > 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) Definitely needs a Fixes: 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) At that point I'd just have the changelog say "a recent commit". > > inadvertently included a line of code to change it without giving any > > reason in the changelog. It is clear that the commit's intention was to > > change KVM_REQ_TLB_FLUSH -> KVM_REQ_TLB_FLUSH_CURRENT, so we don't > > unneedlesly flush other contexts but one of the hunks changed > > nearby KVM_REQ_MMU_SYNC instead. > > > > The this patch changes it back. > > > > Link: https://lore.kernel.org/lkml/20200320212833.3507-26-sean.j.christopherson@intel.com/ > > Cc: Sean Christopherson <sean.j.christopherson@intel.com> > > Cc: Vitaly Kuznetsov <vkuznets@redhat.com> > > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > > --- > > Changed from v1: > > update patch description > > > > arch/x86/kvm/mmu/mmu.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index 4e03841f053d..9a93de921f2b 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, > > } > > > > if (sp->unsync_children) > > - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); > > + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); > > > > __clear_sp_write_flooding_count(sp); > > FWIW, > > Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> > > but it'd be great to hear from Sean). I got nothing, AFAICT I was simply overzealous. Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
On 02/09/20 15:54, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@linux.alibaba.com> > > When kvm_mmu_get_page() gets a page with unsynced children, the spt > pagetable is unsynchronized with the guest pagetable. But the > guest might not issue a "flush" operation on it when the pagetable > entry is changed from zero or other cases. The hypervisor has the > responsibility to synchronize the pagetables. > > The linux kernel behaves as above for many years, But > 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) > inadvertently included a line of code to change it without giving any > reason in the changelog. It is clear that the commit's intention was to > change KVM_REQ_TLB_FLUSH -> KVM_REQ_TLB_FLUSH_CURRENT, so we don't > unneedlesly flush other contexts but one of the hunks changed > nearby KVM_REQ_MMU_SYNC instead. > > The this patch changes it back. > > Link: https://lore.kernel.org/lkml/20200320212833.3507-26-sean.j.christopherson@intel.com/ > Cc: Sean Christopherson <sean.j.christopherson@intel.com> > Cc: Vitaly Kuznetsov <vkuznets@redhat.com> > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > --- > Changed from v1: > update patch description > > arch/x86/kvm/mmu/mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 4e03841f053d..9a93de921f2b 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, > } > > if (sp->unsync_children) > - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); > + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); > > __clear_sp_write_flooding_count(sp); > > Queued, thanks. Paolo
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 4e03841f053d..9a93de921f2b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, } if (sp->unsync_children) - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); __clear_sp_write_flooding_count(sp);