linux-kernel - [PATCH 4.9 090/116] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM

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Message-Id: <20200213151917.983069432@linuxfoundation.org>
Date:   Thu, 13 Feb 2020 07:20:34 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 090/116] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM

From: Sean Christopherson <sean.j.christopherson@...el.com>

[ Upstream commit e30a7d623dccdb3f880fbcad980b0cb589a1da45 ]

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@...r.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/x86.c |    2 --
 1 file changed, 2 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6132,14 +6132,12 @@ static void kvm_set_mmio_spte_mask(void)
 	/* Set the present bit. */
 	mask |= 1ull;
 
-#ifdef CONFIG_X86_64
 	/*
 	 * If reserved bit is not supported, clear the present bit to disable
 	 * mmio page fault.
 	 */
 	if (maxphyaddr == 52)
 		mask &= ~1ull;
-#endif
 
 	kvm_mmu_set_mmio_spte_mask(mask);
 }