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Mon, 04 May 2026 08:45:34 -0700 (PDT) Received: from x1.local ([142.189.10.167]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8fc29a81049sm1190576885a.18.2026.05.04.08.45.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2026 08:45:34 -0700 (PDT) Date: Mon, 4 May 2026 11:45:32 -0400 From: Peter Xu To: Thomas Huth Cc: Paolo Bonzini , kvm@vger.kernel.org, Yi Liu , =?utf-8?Q?Cl=C3=A9ment?= Mathieu--Drif , "Michael S. Tsirkin" Subject: Re: intel_iommu unit test is also failing (was: Re: [PATCH kvm-unit-tests] realmode: load above stack) Message-ID: References: <20240604143507.1041901-1-pbonzini@redhat.com> <8aa24294-439f-4484-b6fc-9327b6fd0306@redhat.com> <600b025e-602e-4128-9679-f53f32b96e8e@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <600b025e-602e-4128-9679-f53f32b96e8e@redhat.com> On Mon, May 04, 2026 at 10:07:25AM +0200, Thomas Huth wrote: > On 04/05/2026 09.58, Thomas Huth wrote: > > On 04/06/2024 16.35, Paolo Bonzini wrote: > > > The bottom 32K of memory are generally reserved for use by the BIOS; > > > for example, traditionally the boot loader is placed at 0x7C00 and > > > the stack grows below that address. > > > > > > It turns out that with some versions of clang, realmode.flat has > > > become big enough that it overlaps the stack used by the multiboot > > > option ROM loader.  The result is that a couple instructions are > > > overwritten.  Typically one or two tests fail and that's it... > > > > > > Move the code above the forbidden region, in real 90s style. > > > > > > Reported-by: Thomas Huth > > > Signed-off-by: Paolo Bonzini > > > --- > > >   x86/realmode.lds | 2 +- > > >   1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/x86/realmode.lds b/x86/realmode.lds > > > index 0ed3063b..e4782a98 100644 > > > --- a/x86/realmode.lds > > > +++ b/x86/realmode.lds > > > @@ -1,6 +1,6 @@ > > >   SECTIONS > > >   { > > > -    . = 16K; > > > +    . = 32K; > > >       stext = .; > > >       .text : { *(.init) *(.text) } > > >       . = ALIGN(4K); > > > >  Hi Paolo! > > > > FYI, the realmode kvm-unit-test now also fails with the recent version > > of GCC 16 for the i386 target: > > > >  https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/jobs/14195195727 > > > > It was working fine some weeks ago with GCC 15.1: > > > >  https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/jobs/13977260961 > > > > When I apply your patch, the problem seems to be gone again in this > > case, but since there were some other issues with this (with older > > versions of GCC, I think): > > > > https://lore.kernel.org/kvm/49f8aadf-6e3f-4d2b-a32a-8ba941a3a2a1@redhat.com/ > > > > ... there must be a better way to fix it? > > > > Could you please have a look? > > By the way, the intel_iommu test now also suddenly started failing (for the > x86_64 target), either due to update of GCC or due to the update from QEMU > v10.2 to 11.0 : > > https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/jobs/14195195728 > > Two weeks ago, it was still working fine: > > https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/jobs/13977260962 Looping in those who take care of qemu's VT-D now (Yi, Clément).. -- Peter Xu