From 9c9384d6d8184ca6d21975ccf4e4f72b560540cc Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Tue, 28 Nov 2017 14:05:19 +0000 Subject: [PATCH] x86/hvm: fix interaction between internal and external emulation A call to handle_hvm_io_completion() is needed for completing I/O that requires external emulation. Such completion should be requested when hvm_vcpu_io_need_completion() returns true after hvm_emulate_once() has completed. This is indicative of the underlying I/O emulation having returned X86EMUL_RETRY and hence a re-emulation of the instruction is needed to pick up the result of the I/O. A call to handle_hvm_io_completion() is NOT needed when the underlying I/O has not returned X86EMUL_RETRY since there will be no result to pick up. Hence it bogus to request such completion when mmio_retry is set, since this can only happen if the underlying I/O emulation has returned X86EMUL_OKAY (meaning the I/O has completed successfully). Reported-by: Andrew Cooper Signed-off-by: Paul Durrant Reviewed-by: Jan Beulich Release-acked-by: Julien Grall --- xen/arch/x86/hvm/io.c | 2 +- xen/arch/x86/hvm/vmx/realmode.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/hvm/io.c b/xen/arch/x86/hvm/io.c index e449b4196e..9d9e1b0e40 100644 --- a/xen/arch/x86/hvm/io.c +++ b/xen/arch/x86/hvm/io.c @@ -88,7 +88,7 @@ bool hvm_emulate_one_insn(hvm_emulate_validate_t *validate, const char *descr) rc = hvm_emulate_one(&ctxt); - if ( hvm_vcpu_io_need_completion(vio) || vio->mmio_retry ) + if ( hvm_vcpu_io_need_completion(vio) ) vio->io_completion = HVMIO_mmio_completion; else vio->mmio_access = (struct npfec){}; diff --git a/xen/arch/x86/hvm/vmx/realmode.c b/xen/arch/x86/hvm/vmx/realmode.c index 03dea6c0fc..11211c8cd8 100644 --- a/xen/arch/x86/hvm/vmx/realmode.c +++ b/xen/arch/x86/hvm/vmx/realmode.c @@ -103,7 +103,7 @@ void vmx_realmode_emulate_one(struct hvm_emulate_ctxt *hvmemul_ctxt) rc = hvm_emulate_one(hvmemul_ctxt); - if ( hvm_vcpu_io_need_completion(vio) || vio->mmio_retry ) + if ( hvm_vcpu_io_need_completion(vio) ) vio->io_completion = HVMIO_realmode_completion; if ( rc == X86EMUL_UNHANDLEABLE ) -- 2.30.2