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[xen master] tools: don't expose XENFEAT_hvm_pirqs by default

Date: Fri, 26 Jan 2024 21:34:02 +0000

Delivery-date: Fri, 26 Jan 2024 21:34:03 +0000

List-id: "Change log for Mercurial \(receive only\)" <xen-changelog.lists.xenproject.org>

commit 024e7131be5ca0cb0a3f68522e490e5882099b00 Author: Roger Pau Monne <roger.pau@xxxxxxxxxx> AuthorDate: Thu Jan 25 10:30:41 2024 +0100 Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> CommitDate: Thu Jan 25 17:46:57 2024 +0000 tools: don't expose XENFEAT_hvm_pirqs by default The HVM pirq feature allows routing interrupts from both physical and emulated devices over event channels, this was done a performance improvement. However its usage is fully undocumented, and the only reference implementation is in Linux. It defeats the purpose of local APIC hardware virtualization, because when using it interrupts avoid the usage of the local APIC altogether. It has also been reported to not work properly with certain devices, at least when using some AMD GPUs Linux attempts to route interrupts over event channels, but Xen doesn't correctly detect such routing, which leads to the hypervisor complaining with: (XEN) d15v0: Unsupported MSI delivery mode 7 for Dom15 When MSIs are attempted to be routed over event channels the entry delivery mode is set to ExtINT, but Xen doesn't detect such routing and attempts to inject the interrupt following the native MSI path, and the ExtINT delivery mode is not supported. Disable HVM PIRQs by default and provide a per-domain option in xl.cfg to enable such feature. Also for backwards compatibility keep the feature enabled for any resumed domains that don't have an explicit selection. Note that the only user of the feature (Linux) is also able to handle native interrupts fine, as the feature was already not used if Xen reported local APIC hardware virtualization active. Link: https://github.com/QubesOS/qubes-issues/issues/7971 Signed-off-by: Roger Pau MonnÃ© <roger.pau@xxxxxxxxxx> Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx> Acked-by: Marek Marczykowski-GÃ³recki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> --- CHANGELOG.md | 2 ++ docs/man/xl.cfg.5.pod.in | 7 +++++++ tools/include/libxl.h | 7 +++++++ tools/libs/light/libxl_create.c | 7 +++++-- tools/libs/light/libxl_types.idl | 1 + tools/libs/light/libxl_x86.c | 12 +++++++++--- tools/python/xen/lowlevel/xc/xc.c | 4 +++- tools/xl/xl_parse.c | 1 + 8 files changed, 35 insertions(+), 6 deletions(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index 723d064254..ddb3ab8db4 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -9,6 +9,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) ### Changed - Changed flexible array definitions in public I/O interface headers to not use "1" as the number of array elements. + - On x86: + - HVM PIRQs are disabled by default. ### Added - On x86: diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in index 2e234b450e..ea8d41727d 100644 --- a/docs/man/xl.cfg.5.pod.in +++ b/docs/man/xl.cfg.5.pod.in @@ -2460,6 +2460,13 @@ The viridian option can be specified as a boolean. A value of true (1) is equivalent to the list [ "defaults" ], and a value of false (0) is equivalent to an empty list. +=item B<hvm_pirq=BOOLEAN> + +Select whether the guest is allowed to route interrupts from devices (either +emulated or passed through) over event channels. + +This option is disabled by default. + =back =head3 Emulated VGA Graphics Device diff --git a/tools/include/libxl.h b/tools/include/libxl.h index 907aa0a330..f1652b1664 100644 --- a/tools/include/libxl.h +++ b/tools/include/libxl.h @@ -608,6 +608,13 @@ * executable in order to not run it as the same user as libxl. */ +/* + * LIBXL_HAVE_HVM_PIRQ indicates the presence of the u.hvm.pirq filed in + * libxl_domain_build_info that signals whether an HVM guest has accesses to + * the XENFEAT_hvm_pirqs feature. + */ +#define LIBXL_HAVE_HVM_PIRQ 1 + /* * libxl memory management * diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c index ce1d431103..0008fac607 100644 --- a/tools/libs/light/libxl_create.c +++ b/tools/libs/light/libxl_create.c @@ -376,6 +376,7 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc, libxl_defbool_setdefault(&b_info->u.hvm.usb, false); libxl_defbool_setdefault(&b_info->u.hvm.vkb_device, true); libxl_defbool_setdefault(&b_info->u.hvm.xen_platform_pci, true); + libxl_defbool_setdefault(&b_info->u.hvm.pirq, false); libxl_defbool_setdefault(&b_info->u.hvm.spice.enable, false); if (!libxl_defbool_val(b_info->u.hvm.spice.enable) && @@ -2375,10 +2376,12 @@ int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config, /* * When restoring (either from a save file or for a migration domain) set - * the MSR relaxed mode for compatibility with older Xen versions if the - * option is not set as part of the original configuration. + * the MSR relaxed mode and HVM PIRQs for compatibility with older Xen + * versions if the options are not set as part of the original + * configuration. */ libxl_defbool_setdefault(&d_config->b_info.arch_x86.msr_relaxed, true); + libxl_defbool_setdefault(&d_config->b_info.u.hvm.pirq, true); return do_domain_create(ctx, d_config, domid, restore_fd, send_back_fd, params, ao_how, aop_console_how); diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl index 7d8bd5d216..899ad30969 100644 --- a/tools/libs/light/libxl_types.idl +++ b/tools/libs/light/libxl_types.idl @@ -692,6 +692,7 @@ libxl_domain_build_info = Struct("domain_build_info",[ ("rdm", libxl_rdm_reserve), ("rdm_mem_boundary_memkb", MemKB), ("mca_caps", uint64), + ("pirq", libxl_defbool), ])), ("pv", Struct(None, [("kernel", string, {'deprecated_by': 'kernel'}), ("slack_memkb", MemKB), diff --git a/tools/libs/light/libxl_x86.c b/tools/libs/light/libxl_x86.c index d16573e72c..a50ec37eb3 100644 --- a/tools/libs/light/libxl_x86.c +++ b/tools/libs/light/libxl_x86.c @@ -9,6 +9,8 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc, switch(d_config->c_info.type) { case LIBXL_DOMAIN_TYPE_HVM: config->arch.emulation_flags = (XEN_X86_EMU_ALL & ~XEN_X86_EMU_VPCI); + if (!libxl_defbool_val(d_config->b_info.u.hvm.pirq)) + config->arch.emulation_flags &= ~XEN_X86_EMU_USE_PIRQ; break; case LIBXL_DOMAIN_TYPE_PVH: config->arch.emulation_flags = XEN_X86_EMU_LAPIC; @@ -864,15 +866,19 @@ void libxl__arch_update_domain_config(libxl__gc *gc, const libxl_domain_config *src) { /* - * Force MSR relaxed to be set (either to true or false) so it's part of - * the domain configuration when saving or performing a live-migration. + * Force MSR relaxed and HVM pirq to be set (either to true or false) so + * it's part of the domain configuration when saving or performing a + * live-migration. * - * Doing so allows the recovery side to figure out whether the flag should + * Doing so allows the recovery side to figure out whether the flags should * be set to true in order to keep backwards compatibility with already * started domains. */ libxl_defbool_setdefault(&dst->b_info.arch_x86.msr_relaxed, libxl_defbool_val(src->b_info.arch_x86.msr_relaxed)); + if (src->c_info.type == LIBXL_DOMAIN_TYPE_HVM ) + libxl_defbool_setdefault(&dst->b_info.u.hvm.pirq, + libxl_defbool_val(src->b_info.u.hvm.pirq)); } /* diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c index d3ea350e07..9feb12ae2b 100644 --- a/tools/python/xen/lowlevel/xc/xc.c +++ b/tools/python/xen/lowlevel/xc/xc.c @@ -159,7 +159,9 @@ static PyObject *pyxc_domain_create(XcObject *self, #if defined (__i386) || defined(__x86_64__) if ( config.flags & XEN_DOMCTL_CDF_hvm ) - config.arch.emulation_flags = (XEN_X86_EMU_ALL & ~XEN_X86_EMU_VPCI); + config.arch.emulation_flags = XEN_X86_EMU_ALL & + ~(XEN_X86_EMU_VPCI | + XEN_X86_EMU_USE_PIRQ); #elif defined (__arm__) || defined(__aarch64__) config.arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE; #else diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c index ed983200c3..9b358f11b8 100644 --- a/tools/xl/xl_parse.c +++ b/tools/xl/xl_parse.c @@ -1801,6 +1801,7 @@ void parse_config_data(const char *config_source, xlu_cfg_get_defbool(config, "hpet", &b_info->u.hvm.hpet, 0); xlu_cfg_get_defbool(config, "vpt_align", &b_info->u.hvm.vpt_align, 0); xlu_cfg_get_defbool(config, "apic", &b_info->apic, 0); + xlu_cfg_get_defbool(config, "hvm_pirq", &b_info->u.hvm.pirq, 0); switch (xlu_cfg_get_list(config, "viridian", &viridian, &num_viridian, 1)) -- generated by git-patchbot for /home/xen/git/xen.git#master

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