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Thu, 08 Aug 2024 06:42:56 -0700 (PDT) From: Alejandro Vallejo To: Xen-devel Cc: Alejandro Vallejo , Jan Beulich , Andrew Cooper , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Anthony PERARD , Juergen Gross Subject: [PATCH v5 00/10] x86: Expose consistent topology to guests Date: Thu, 8 Aug 2024 14:42:40 +0100 Message-ID: <20240808134251.29995-1-alejandro.vallejo@cloud.com> X-Mailer: git-send-email 2.45.2 MIME-Version: 1.0 v4 -> v5: Largely unchanged and resent for review after the 4.20 dev cycle started. * Addressed Andrew's nits in v4/patch1 * Addressed Jan's concern with MTRR overrides in v4/patch6 by keeping the same MTRR data in the vCPU contexts for HVM domain creations. v4: https://lore.kernel.org/xen-devel/cover.1719416329.git.alejandro.vallejo@cloud.com/ v3 -> v4: * Fixed cpuid() bug in hvmloader, causing UB in v3 * Fixed a bogus assert in hvmloader, also causing a crash in v3 * Used HVM contexts rather than sync'd algos between Xen and toolstack in order to initialise the per-vCPU LAPIC state. * Formatting asjustments. v3: https://lore.kernel.org/xen-devel/cover.1716976271.git.alejandro.vallejo@cloud.com/ v2 -> v3: (v2/patch2 and v2/patch4 are already committed) * Moved the vlapic check hook addition to v3/patch1 * And created a check hook for the architectural state too for consistency. * Fixed migrations from Xen <= 4.13 by reconstructing the previous topology. * Correctly set the APIC ID after a policy change when vlapic is already in x2APIC mode. * Removed bogus assumption introduced in v1 and v2 on hvmloader about which 8bit APIC IDs represent ids > 254. (it's "id % 0xff", not "min(id, 0xff)". * Used an x2apic flag check instead. * Various formatting adjustments. v2: https://lore.kernel.org/xen-devel/cover.1715102098.git.alejandro.vallejo@cloud.com/ v1 -> v2: * v1/patch 4 replaced by a different strategy (See patches 4 and 5 in v2): * Have hvmloader populate MADT with the real APIC IDs as read by the APs themselves rather than giving it knowledge on how to derive them. * Removed patches 2 and 3 in v1, as no longer relevant. * Split v1/patch6 in two parts ((a) creating the generator and (b) plugging it in) and use the generator in the unit tests of the vcpuid->apicid mapping function. Becomes patches 6 and 8 in v2. Patch 1: Same as v1/patch1. Patch 2: Header dependency cleanup in preparation for patch3. Patch 3: Adds vlapic_hidden check for the newly introduced reserved area. Patch 4: [hvmloader] Replaces INIT+SIPI+SIPI sequences with hypercalls. Patch 5: [hvmloader] Retrieve the per-CPU APIC IDs from the APs themselves. Patch 6: Split from v1/patch6. Patch 7: Logically matching v1/patch5, but using v2/patch6 for testing. Patch 8: Split from v1/patch6. v1: https://lore.kernel.org/xen-devel/20240109153834.4192-1-alejandro.vallejo@cloud.com/ === Original cover letter === Current topology handling is close to non-existent. As things stand, APIC IDs are allocated through the apic_id=vcpu_id*2 relation without giving any hints to the OS on how to parse the x2APIC ID of a given CPU and assuming the guest will assume 2 threads per core. This series involves bringing x2APIC IDs into the migration stream, so older guests keep operating as they used to and enhancing Xen+toolstack so new guests get topology information consistent with their x2APIC IDs. As a side effect of this, x2APIC IDs are now packed and don't have (unless under a pathological case) gaps. Further work ought to allow combining this topology configurations with gang-scheduling of guest hyperthreads into affine physical hyperthreads. For the time being it purposefully keeps the configuration of "1 socket" + "1 thread per core" + "1 core per vCPU". Patch 1: Includes x2APIC IDs in the migration stream. This allows Xen to reconstruct the right x2APIC IDs on migrated-in guests, and future-proofs itself in the face of x2APIC ID derivation changes. Patch 2: Minor refactor to expose xc_cpu_policy in libxl Patch 3: Refactors xen/lib/x86 to work on non-Xen freestanding environments (e.g: hvmloader) Patch 4: Remove old assumptions about vcpu_id<->apic_id relationship in hvmloader Patch 5: Add logic to derive x2APIC IDs given a CPU policy and vCPU IDs Patch 6: Includes a simple topology generator for toolstack so new guests have topologically consistent information in CPUID Alejandro Vallejo (10): tools/hvmloader: Fix non-deterministic cpuid() x86/vlapic: Move lapic migration checks to the check hooks xen/x86: Add initial x2APIC ID to the per-vLAPIC save area xen/x86: Add supporting code for uploading LAPIC contexts during domain create tools/hvmloader: Retrieve (x2)APIC IDs from the APs themselves tools/libguest: Always set vCPU context in vcpu_hvm() xen/lib: Add topology generator for x86 xen/x86: Derive topologically correct x2APIC IDs from the policy tools/libguest: Set distinct x2APIC IDs for each vCPU xen/x86: Synthesise domain topologies tools/firmware/hvmloader/config.h | 6 +- tools/firmware/hvmloader/hvmloader.c | 4 +- tools/firmware/hvmloader/smp.c | 54 ++++-- tools/firmware/hvmloader/util.c | 9 - tools/firmware/hvmloader/util.h | 27 ++- tools/include/xen-tools/common-macros.h | 5 + tools/libs/guest/xg_cpuid_x86.c | 24 ++- tools/libs/guest/xg_dom_x86.c | 114 ++++++++----- tools/tests/cpu-policy/test-cpu-policy.c | 201 +++++++++++++++++++++++ xen/arch/x86/cpu-policy.c | 9 +- xen/arch/x86/cpuid.c | 14 +- xen/arch/x86/hvm/vlapic.c | 123 ++++++++++---- xen/arch/x86/include/asm/hvm/vlapic.h | 1 + xen/include/public/arch-x86/hvm/save.h | 2 + xen/include/xen/lib/x86/cpu-policy.h | 27 +++ xen/lib/x86/policy.c | 164 ++++++++++++++++++ xen/lib/x86/private.h | 4 + 17 files changed, 683 insertions(+), 105 deletions(-)