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To: Bjorn Helgaas Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, thomas.lendacky@amd.com, ardb@kernel.org, tzimmermann@suse.de, bhelgaas@google.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Updating es_em_ctxt fi to zero Message-ID: References: <20241119180517.196079-2-ragavendra.bn@gmail.com> <20241119192602.GA2272685@bhelgaas> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241119192602.GA2272685@bhelgaas> On Tue, Nov 19, 2024 at 01:26:02PM -0600, Bjorn Helgaas wrote: > On Tue, Nov 19, 2024 at 10:05:18AM -0800, Ragavendra wrote: > > Updating es_em_ctxt to zero for the ctxt->fi variable in > > verify_exception_info when ES_EXCEPTION is returned. > > This commit log basically says in English what the code does in C. If > you can include the *reason* why this is important, it will be more > helpful. For example, maybe somebody consumes other parts of ctxt.fi > (a struct es_fault_info), and without this patch, they use junk that > causes an oops or some other bad thing. > > If the 34ff65901735 Fixes: tag is correct, I suppose the problem > happens because ctxt is allocated on the stack and contains junk, and > then svsm_perform_ghcb_protocol() passes it on to > vc_forward_exception(), which does use fields of ctxt->fi other than > .vector, which will be junk without this patch. > > Hints and samples for commit logs: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/maintainer-tip.rst?id=v6.11#n134 > > Based on "git log --oneline arch/x86/coco/sev", I would expect the > subject line to have an "x86/sev: " prefix, e.g., > > x86/sev: Clear es_em_ctxt.fi to ... > > > Fixes: 34ff65901735 x86/sev: Use kernel provided SVSM Calling Areas > > Signed-off-by: Ragavendra Nagraj > > --- > > arch/x86/coco/sev/shared.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/x86/coco/sev/shared.c b/arch/x86/coco/sev/shared.c > > index 71de53194089..b8540d85e6f0 100644 > > --- a/arch/x86/coco/sev/shared.c > > +++ b/arch/x86/coco/sev/shared.c > > @@ -239,6 +239,8 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt > > if ((info & SVM_EVTINJ_VALID) && > > ((v == X86_TRAP_GP) || (v == X86_TRAP_UD)) && > > ((info & SVM_EVTINJ_TYPE_MASK) == SVM_EVTINJ_TYPE_EXEPT)) { > > + memset(&ctxt->fi, 0, sizeof(ctxt->fi)); > > + > > ctxt->fi.vector = v; > > > > if (info & SVM_EVTINJ_VALID_ERR) > > -- > > 2.46.1 > > Yes Bjorn, I completely agree with the need to update the reason, I will update the commit log and send the newer version accordingly. -- Thanks & regards, Ragavendra N