linux-kernel - [PATCH v2 09/25] x86/fault: Dump RMP table information when RMP page faults occur

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Date: Thu, 25 Jan 2024 22:11:09 -0600
From: Michael Roth <michael.roth@....com>
To: <x86@...nel.org>
CC: <kvm@...r.kernel.org>, <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
	<linux-crypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
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Subject: [PATCH v2 09/25] x86/fault: Dump RMP table information when RMP page faults occur

RMP faults on kernel addresses are fatal and should never happen in
practice. They indicate a bug in the host kernel somewhere. Userspace
RMP faults shouldn't occur either, since even for VMs the memory used
for private pages is handled by guest_memfd and by design is not
mappable by userspace.

Dump RMP table information about the PFN corresponding to the faulting
HVA to help diagnose any issues of this sort when show_fault_oops() is
triggered by an RMP fault.

Signed-off-by: Michael Roth <michael.roth@....com>
---
 arch/x86/mm/fault.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 8805e2e20df6..859adcd123c9 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -34,6 +34,7 @@
 #include <asm/kvm_para.h>		/* kvm_handle_async_pf		*/
 #include <asm/vdso.h>			/* fixup_vdso_exception()	*/
 #include <asm/irq_stack.h>
+#include <asm/sev.h>			/* snp_dump_hva_rmpentry()	*/
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -580,6 +581,9 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
 	}
 
 	dump_pagetable(address);
+
+	if (error_code & X86_PF_RMP)
+		snp_dump_hva_rmpentry(address);
 }
 
 static noinline void
-- 
2.25.1