linux-kernel - [PATCH v4 4/4] kvm: x86: Allow to respond to generic signals during slow PF

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Message-Id: <20221011195947.557281-1-peterx@redhat.com>
Date:   Tue, 11 Oct 2022 15:59:47 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     peterx@...hat.com, David Matlack <dmatlack@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM Mailing List <linux-mm@...ck.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH v4 4/4] kvm: x86: Allow to respond to generic signals during slow PF

Enable x86 slow page faults to be able to respond to non-fatal signals,
returning -EINTR properly when it happens.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index cc26f425f41c..83b9c034313d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3148,8 +3148,13 @@ static void kvm_send_hwpoison_signal(unsigned long address, struct task_struct *
 	send_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, PAGE_SHIFT, tsk);
 }
 
-static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn)
+static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, gfn_t gfn, kvm_pfn_t pfn)
 {
+	if (is_sigpending_pfn(pfn)) {
+		kvm_handle_signal_exit(vcpu);
+		return -EINTR;
+	}
+
 	/*
 	 * Do not cache the mmio info caused by writing the readonly gfn
 	 * into the spte otherwise read access on readonly gfn also can
@@ -3171,7 +3176,7 @@ static int handle_abnormal_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fau
 {
 	/* The pfn is invalid, report the error! */
 	if (unlikely(is_error_pfn(fault->pfn)))
-		return kvm_handle_bad_page(vcpu, fault->gfn, fault->pfn);
+		return kvm_handle_error_pfn(vcpu, fault->gfn, fault->pfn);
 
 	if (unlikely(!fault->slot)) {
 		gva_t gva = fault->is_tdp ? 0 : fault->addr;
@@ -4186,7 +4191,12 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 		}
 	}
 
-	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, NULL,
+	/*
+	 * Allow gup to bail on pending non-fatal signals when it's also allowed
+	 * to wait for IO.  Note, gup always bails if it is unable to quickly
+	 * get a page and a fatal signal, i.e. SIGKILL, is pending.
+	 */
+	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, true, NULL,
 					  fault->write, &fault->map_writable,
 					  &fault->hva);
 	return RET_PF_CONTINUE;
-- 
2.37.3