* [PATCH] x86/PVH: restore VMX APIC assist for Dom0
@ 2022-08-23 11:56 Jan Beulich
2022-09-20 13:05 ` Roger Pau Monné
0 siblings, 1 reply; 2+ messages in thread
From: Jan Beulich @ 2022-08-23 11:56 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Wei Liu, Roger Pau Monné, Jane Malalane
I don't expect it was intended to default PVH Dom0 to "no assist" mode.
Introduce command line (sub-)options allowing to suppress enabling of
the assists, paralleling the guest config settings for DomU, but restore
the defaulting to "enabled".
Fixes: 2ce11ce249a3 ("x86/HVM: allow per-domain usage of hardware virtualized APIC")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
Besides the issue caused here (the manifestation of which appears to
correlate with the other fallout Andrew is trying to deal with) I'm
observing further warnings, but I guess these have been there for some
time (perhaps forever): When parsing AML and encountering the objects
describing the CPUs, Linux would find entries with the original APIC
IDs. If those don't match the ones we assign in pvh_setup_acpi_madt(),
the kernel will wrongly consider the entries to describe further CPUs,
which it therefore would deem hot-pluggable. This again results in
warnings, this time "NR_CPUS/possible_cpus limit of ... reached".
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -753,7 +753,8 @@ Specify the bit width of the DMA heap.
### dom0
= List of [ pv | pvh, shadow=<bool>, verbose=<bool>,
- cpuid-faulting=<bool>, msr-relaxed=<bool> ]
+ cpuid-faulting=<bool>, msr-relaxed=<bool>,
+ assisted-xapic=<bool>, assisted-x2apic=<bool> ]
Applicability: x86
@@ -814,6 +815,10 @@ Controls for how dom0 is constructed on
If using this option is necessary to fix an issue, please report a bug.
+* The `assisted-xapic` and `assisted-x2apic` options, defaulting to true,
+ allow disabling of the respective hardware assists. These are applicable
+ to PVH Dom0 only, and their effect is limited to VT-x.
+
### dom0-cpuid
= List of comma separated booleans
--- a/xen/arch/x86/dom0_build.c
+++ b/xen/arch/x86/dom0_build.c
@@ -293,6 +293,12 @@ static int __init cf_check parse_dom0_pa
opt_dom0_cpuid_faulting = val;
else if ( (val = parse_boolean("msr-relaxed", s, ss)) >= 0 )
opt_dom0_msr_relaxed = val;
+#ifdef CONFIG_HVM
+ else if ( (val = parse_boolean("assisted-xapic", s, ss)) >= 0 )
+ opt_dom0_assisted_xapic = val;
+ else if ( (val = parse_boolean("assisted-x2apic", s, ss)) >= 0 )
+ opt_dom0_assisted_x2apic = val;
+#endif
else
rc = -EINVAL;
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -55,6 +55,9 @@
*/
#define HVM_VM86_TSS_SIZE 265
+bool __initdata opt_dom0_assisted_xapic = true;
+bool __initdata opt_dom0_assisted_x2apic = true;
+
static unsigned int __initdata acpi_intr_overrides;
static struct acpi_madt_interrupt_override __initdata *intsrcovr;
--- a/xen/arch/x86/include/asm/setup.h
+++ b/xen/arch/x86/include/asm/setup.h
@@ -68,6 +68,14 @@ extern bool opt_dom0_verbose;
extern bool opt_dom0_cpuid_faulting;
extern bool opt_dom0_msr_relaxed;
+#ifdef CONFIG_HVM
+extern bool opt_dom0_assisted_xapic;
+extern bool opt_dom0_assisted_x2apic;
+#else
+#define opt_dom0_assisted_xapic false
+#define opt_dom0_assisted_x2apic false
+#endif
+
#define max_init_domid (0)
#endif
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -784,6 +784,11 @@ static struct domain *__init create_dom0
dom0_cfg.arch.emulation_flags |=
XEN_X86_EMU_LAPIC | XEN_X86_EMU_IOAPIC | XEN_X86_EMU_VPCI;
+
+ if ( opt_dom0_assisted_xapic )
+ dom0_cfg.arch.misc_flags |= XEN_X86_ASSISTED_XAPIC;
+ if ( opt_dom0_assisted_x2apic )
+ dom0_cfg.arch.misc_flags |= XEN_X86_ASSISTED_X2APIC;
}
if ( iommu_enabled )
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] x86/PVH: restore VMX APIC assist for Dom0
2022-08-23 11:56 [PATCH] x86/PVH: restore VMX APIC assist for Dom0 Jan Beulich
@ 2022-09-20 13:05 ` Roger Pau Monné
0 siblings, 0 replies; 2+ messages in thread
From: Roger Pau Monné @ 2022-09-20 13:05 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel, Andrew Cooper, Wei Liu, Jane Malalane
On Tue, Aug 23, 2022 at 01:56:22PM +0200, Jan Beulich wrote:
> --- a/xen/arch/x86/hvm/dom0_build.c
> +++ b/xen/arch/x86/hvm/dom0_build.c
> @@ -55,6 +55,9 @@
> */
> #define HVM_VM86_TSS_SIZE 265
>
> +bool __initdata opt_dom0_assisted_xapic = true;
> +bool __initdata opt_dom0_assisted_x2apic = true;
Defaulting those to true unconditionally is troublesome, as the check
in arch_sanitise_domain_config() will fail if either
assisted_x{2,}apic_available is not true, and dom0 domain creation
will fail, so...
> +
> static unsigned int __initdata acpi_intr_overrides;
> static struct acpi_madt_interrupt_override __initdata *intsrcovr;
>
> --- a/xen/arch/x86/include/asm/setup.h
> +++ b/xen/arch/x86/include/asm/setup.h
> @@ -68,6 +68,14 @@ extern bool opt_dom0_verbose;
> extern bool opt_dom0_cpuid_faulting;
> extern bool opt_dom0_msr_relaxed;
>
> +#ifdef CONFIG_HVM
> +extern bool opt_dom0_assisted_xapic;
> +extern bool opt_dom0_assisted_x2apic;
> +#else
> +#define opt_dom0_assisted_xapic false
> +#define opt_dom0_assisted_x2apic false
> +#endif
> +
> #define max_init_domid (0)
>
> #endif
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -784,6 +784,11 @@ static struct domain *__init create_dom0
>
> dom0_cfg.arch.emulation_flags |=
> XEN_X86_EMU_LAPIC | XEN_X86_EMU_IOAPIC | XEN_X86_EMU_VPCI;
> +
> + if ( opt_dom0_assisted_xapic )
> + dom0_cfg.arch.misc_flags |= XEN_X86_ASSISTED_XAPIC;
> + if ( opt_dom0_assisted_x2apic )
> + dom0_cfg.arch.misc_flags |= XEN_X86_ASSISTED_X2APIC;
...the values of assisted_x{2,}apic_available need to be taken into
account here in order to avoid requesting an invalid configuration.
I could swear I have checked PVH dom0 interaction when reviewing the
original patch, but I clearly missed it.
Thanks, Roger.
^ permalink raw reply [flat|nested] 2+ messages in thread
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