linux-kernel - [PATCH v3 5/8] KVM: Do not incorporate page offset into gfn=>pfn cache user address

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Message-Id: <20220429210025.3293691-6-seanjc@google.com>
Date:   Fri, 29 Apr 2022 21:00:22 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Mingwei Zhang <mizhang@...gle.com>
Subject: [PATCH v3 5/8] KVM: Do not incorporate page offset into gfn=>pfn
 cache user address

Don't adjust the userspace address in the gfn=>pfn cache by the page
offset from the gpa.  KVM should never use the user address directly, and
all KVM operations that translate a user address to something else
require the user address to be page aligned.  Ignoring the offset will
allow the cache to reuse a gfn=>hva translation in the unlikely event
that the page offset of the gpa changes, but the gfn does not.  And more
importantly, not having to (un)adjust the user address will simplify a
future bug fix.

Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 virt/kvm/pfncache.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 40cbe90d52e0..05cb0bcbf662 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -179,8 +179,6 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
 			ret = -EFAULT;
 			goto out;
 		}
-
-		gpc->uhva += page_offset;
 	}

 	/*
-- 
2.36.0.464.gb9c8b46e94-goog