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AJvYcCXjG61WfV0+Qz06qvuXnpijxLGe7zkLOOIjh/utrPIwDyTRIgRPjAH7WPTw8DmYxc4aD3JtX88g1TU=@lists.xenproject.org X-Gm-Message-State: AOJu0YwyvAEzx77R/CBaJbehkjKh54cQPl8kQX+00G4Xwyp24g0nHHtz NsSaA/xrGfoyGgM0gW/rHt6ZNGcw8+iBTfbeEo+He3UISUJ1V4eryd4YJUvGOof9hpwIBuRMswD 6X0k= X-Gm-Gg: ASbGncsPWqRXQs8qFK6hsDLpZ+owywIpG+Edj3l/bRtSh2SvZKlDpH8sBgQQ6S7yWjj 32djRAGAaBR32Wb/oldtFEiK70YgStX4vqx724px3SJIC6/wPD+haOUaRuIKm+GA7U8v3+4/CFR M6SwtHpY/ok5p+B1eQx+SIgIBNEwPB3Kw/mEmcb/fOl57goJTcM2frqHf/YtB1gAkvT/iqUAdDK 7hVfgXLK1oEdLVfGjoUe2bgBXi2ORJrNtBgnPB8n2fK5gHUcc9PUaw5fEhy9TfH3GM1RWBBEXZf GYVqpLkxLcp1/PDLhm5hBV+HPeuYhbDkbhCe2q4Tkl8T8X+gVF8= X-Google-Smtp-Source: AGHT+IG2adtEzPJsUBOh3ZFuOSLZfOKqlIR2xFoxwrtMpZSO3oFAgkcovhJZOzgowr/MtDwzRgKI9w== X-Received: by 2002:a05:600c:470c:b0:43c:f050:fed3 with SMTP id 5b1f17b1804b1-43cf051022dmr92439915e9.11.1741684673845; Tue, 11 Mar 2025 02:17:53 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 11 Mar 2025 09:17:52 +0000 Message-Id: Cc: "Andrew Cooper" , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , "Anthony PERARD" , "Juergen Gross" , Subject: Re: [PATCH] tools: Mark ACPI SDTs as NVS in the PVH build path From: "Alejandro Vallejo" To: "Jan Beulich" X-Mailer: aerc 0.18.2 References: <20250310152523.81181-1-alejandro.vallejo@cloud.com> <5f207284-d206-417a-b963-c922119abe33@suse.com> In-Reply-To: <5f207284-d206-417a-b963-c922119abe33@suse.com> On Tue Mar 11, 2025 at 8:30 AM GMT, Jan Beulich wrote: > On 10.03.2025 16:25, Alejandro Vallejo wrote: > > Commit cefeffc7e583 marked ACPI tables as NVS in the hvmloader path > > because SeaBIOS may otherwise just mark it as RAM. There is, however, > > yet another reason to do it even in the PVH path. Xen's incarnation of > > AML relies on having access to some ACPI tables (e.g: _STA of Processor > > objects relies on reading the processor online bit in its MADT entry) > >=20 > > This is problematic if the OS tries to reclaim ACPI memory for page > > tables as it's needed for runtime and can't be reclaimed after the OSPM > > is up and running. > >=20 > > Fixes: de6d188a519f("hvmloader: flip "ACPI data" to "ACPI NVS" type for= ACPI table region)" > > Signed-off-by: Alejandro Vallejo > > --- > > I really, really, really dislike this idea of accessing the MADT from > > AML. > > I think this isn't Xen's invention, but something I've seen in various > systems' AML. > Do you mean ACPI hotplug? I don't think I've ever seen a real system with support for it. I don't suppose you remember any specifically? I'd be quite interested to have a look at their ACPI dumps. > > In time I'll try to implement something to stop doing it, but for > > the time being I find it preferable to align libxl to hvmloader rather > > than trying to restrict what's reclaimable and what isn't. > > --- > > tools/firmware/hvmloader/e820.c | 4 ++++ > > tools/libs/light/libxl_x86.c | 2 +- > > 2 files changed, 5 insertions(+), 1 deletion(-) > >=20 > > diff --git a/tools/firmware/hvmloader/e820.c b/tools/firmware/hvmloader= /e820.c > > index c490a0bc790c..86d39544e887 100644 > > --- a/tools/firmware/hvmloader/e820.c > > +++ b/tools/firmware/hvmloader/e820.c > > @@ -210,6 +210,10 @@ int build_e820_table(struct e820entry *e820, > > * space reuse by an ACPI unaware / buggy bootloader, option ROM, = etc. > > * before an ACPI OS takes control. This is possible due to the fa= ct that > > * ACPI NVS memory is explicitly described as non-reclaimable in A= CPI spec. > > + * > > + * Furthermore, Xen relies on accessing ACPI tables from within th= e AML > > + * code exposed to guests. So Xen's ACPI tables are not, in genera= l, > > + * reclaimable. > > */ > > =20 > > if ( acpi_enabled ) > > diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.= c > > index a3164a3077fe..265da8072a59 100644 > > --- a/tools/libs/light/libxl_x86.c > > +++ b/tools/libs/light/libxl_x86.c > > @@ -742,7 +742,7 @@ static int domain_construct_memmap(libxl__gc *gc, > > e820[nr].addr =3D dom->acpi_modules[i].guest_addr_out & ~(= page_size - 1); > > e820[nr].size =3D dom->acpi_modules[i].length + > > (dom->acpi_modules[i].guest_addr_out & (page_size - 1)= ); > > - e820[nr].type =3D E820_ACPI; > > + e820[nr].type =3D E820_NVS; > > This likely needs a comment then, too. Fair enough. Let me send a v2 with that. > > Jan Cheers, Alejandro