FAILED: patch "[PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM" failed to apply to 5.4-stable tree

FAILED: patch "[PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM" failed to apply to 5.4-stable tree

[gregkh]

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e30a7d623dccdb3f880fbcad980b0cb589a1da45 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Tue, 7 Jan 2020 16:12:10 -0800
Subject: [PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM

Remove the bogus 64-bit only condition from the check that disables MMIO
spte optimization when the system supports the max PA, i.e. doesn't have
any reserved PA bits.  32-bit KVM always uses PAE paging for the shadow
MMU, and per Intel's SDM:

  PAE paging translates 32-bit linear addresses to 52-bit physical
  addresses.

The kernel's restrictions on max physical addresses are limits on how
much memory the kernel can reasonably use, not what physical addresses
are supported by hardware.

Fixes: ce88decffd17 ("KVM: MMU: mmio page fault support")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2992ff7b42a7..57e4dbddba72 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6193,7 +6193,7 @@ static void kvm_set_mmio_spte_mask(void)
 	 * If reserved bit is not supported, clear the present bit to disable
 	 * mmio page fault.
 	 */
-	if (IS_ENABLED(CONFIG_X86_64) && shadow_phys_bits == 52)
+	if (shadow_phys_bits == 52)
 		mask &= ~1ull;
 
 	kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);

Re: FAILED: patch "[PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM" failed to apply to 5.4-stable tree

[Sasha Levin]

On Sun, Feb 09, 2020 at 01:26:43PM +0100, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 5.4-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From e30a7d623dccdb3f880fbcad980b0cb589a1da45 Mon Sep 17 00:00:00 2001
>From: Sean Christopherson <sean.j.christopherson@intel.com>
>Date: Tue, 7 Jan 2020 16:12:10 -0800
>Subject: [PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM
>
>Remove the bogus 64-bit only condition from the check that disables MMIO
>spte optimization when the system supports the max PA, i.e. doesn't have
>any reserved PA bits.  32-bit KVM always uses PAE paging for the shadow
>MMU, and per Intel's SDM:
>
>  PAE paging translates 32-bit linear addresses to 52-bit physical
>  addresses.
>
>The kernel's restrictions on max physical addresses are limits on how
>much memory the kernel can reasonably use, not what physical addresses
>are supported by hardware.
>
>Fixes: ce88decffd17 ("KVM: MMU: mmio page fault support")
>Cc: stable@vger.kernel.org
>Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Conflicts when rebasing back are mostly due to file or variable renames.
I've fixed it and queued for 5.4-4.4.

-- 
Thanks,
Sasha