kernel/arch/x86/hyperv/hv_crash.c, branch master

x86/hyperv: Use any general-purpose register when saving %cr2 and %cr8

2026-03-12T04:25:20Z

hv_hvcrash_ctxt_save() in arch/x86/hyperv/hv_crash.c currently saves %cr2 and %cr8 using %eax ("=a"). This unnecessarily forces a specific register. Update the inline assembly to use a general-purpose register ("=r") for both %cr2 and %cr8. This makes the code more flexible for the compiler while producing the same saved context contents. No functional changes. Signed-off-by: Uros Bizjak Cc: K. Y. Srinivasan Cc: Haiyang Zhang Cc: Wei Liu Cc: Dexuan Cui Cc: Long Li Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Signed-off-by: Wei Liu

x86/hyperv: Use current_stack_pointer to avoid asm() in hv_hvcrash_ctxt_save()

2026-03-12T04:25:19Z

Use current_stack_pointer to avoid asm() when saving %rsp to the crash context memory in hv_hvcrash_ctxt_save(). The new code is more readable and results in exactly the same object file. Signed-off-by: Uros Bizjak Cc: K. Y. Srinivasan Cc: Haiyang Zhang Cc: Wei Liu Cc: Dexuan Cui Cc: Long Li Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Signed-off-by: Wei Liu

x86/hyperv: Save segment registers directly to memory in hv_hvcrash_ctxt_save()

2026-03-12T04:25:19Z

hv_hvcrash_ctxt_save() in arch/x86/hyperv/hv_crash.c currently saves segment registers via a general-purpose register (%eax). Update the code to save segment registers (cs, ss, ds, es, fs, gs) directly to the crash context memory using movw. This avoids unnecessary use of a general-purpose register, making the code simpler and more efficient. The size of the corresponding object file improves as follows: text data bss dec hex filename 4167 176 200 4543 11bf hv_crash-old.o 4151 176 200 4527 11af hv_crash-new.o No functional change occurs to the saved context contents; this is purely a code-quality improvement. Signed-off-by: Uros Bizjak Cc: K. Y. Srinivasan Cc: Haiyang Zhang Cc: Wei Liu Cc: Dexuan Cui Cc: Long Li Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Signed-off-by: Wei Liu

x86/hyperv: Use __naked attribute to fix stackless C function

2026-03-11T16:54:24Z

hv_crash_c_entry() is a C function that is entered without a stack, and this is only allowed for functions that have the __naked attribute, which informs the compiler that it must not emit the usual prologue and epilogue or emit any other kind of instrumentation that relies on a stack frame. So split up the function, and set the __naked attribute on the initial part that sets up the stack, GDT, IDT and other pieces that are needed for ordinary C execution. Given that function calls are not permitted either, use the existing long return coded in an asm() block to call the second part of the function, which is an ordinary function that is permitted to call other functions as usual. Reviewed-by: Andrew Cooper # asm parts, not hv parts Reviewed-by: Mukesh Rathor Acked-by: Uros Bizjak Cc: Wei Liu Cc: linux-hyperv@vger.kernel.org Fixes: 94212d34618c ("x86/hyperv: Implement hypervisor RAM collection into vmcore") Signed-off-by: Ard Biesheuvel Signed-off-by: Wei Liu

Merge tag 'hyperv-next-signed-20260218' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2026-02-20T16:48:31Z

Pull Hyper-V updates from Wei Liu: - Debugfs support for MSHV statistics (Nuno Das Neves) - Support for the integrated scheduler (Stanislav Kinsburskii) - Various fixes for MSHV memory management and hypervisor status handling (Stanislav Kinsburskii) - Expose more capabilities and flags for MSHV partition management (Anatol Belski, Muminul Islam, Magnus Kulke) - Miscellaneous fixes to improve code quality and stability (Carlos López, Ethan Nelson-Moore, Li RongQing, Michael Kelley, Mukesh Rathor, Purna Pavan Chandra Aekkaladevi, Stanislav Kinsburskii, Uros Bizjak) - PREEMPT_RT fixes for vmbus interrupts (Jan Kiszka) * tag 'hyperv-next-signed-20260218' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: (34 commits) mshv: Handle insufficient root memory hypervisor statuses mshv: Handle insufficient contiguous memory hypervisor status mshv: Introduce hv_deposit_memory helper functions mshv: Introduce hv_result_needs_memory() helper function mshv: Add SMT_ENABLED_GUEST partition creation flag mshv: Add nested virtualization creation flag Drivers: hv: vmbus: Simplify allocation of vmbus_evt mshv: expose the scrub partition hypercall mshv: Add support for integrated scheduler mshv: Use try_cmpxchg() instead of cmpxchg() x86/hyperv: Fix error pointer dereference x86/hyperv: Reserve 3 interrupt vectors used exclusively by MSHV Drivers: hv: vmbus: Use kthread for vmbus interrupts on PREEMPT_RT x86/hyperv: Remove ASM_CALL_CONSTRAINT with VMMCALL insn x86/hyperv: Use savesegment() instead of inline asm() to save segment registers mshv: fix SRCU protection in irqfd resampler ack handler mshv: make field names descriptive in a header struct x86/hyperv: Update comment in hyperv_cleanup() mshv: clear eventfd counter on irqfd shutdown x86/hyperv: Use memremap()/memunmap() instead of ioremap_cache()/iounmap() ...

x86/hyperv: fix a compiler warning in hv_crash.c

2026-02-04T06:11:38Z

Fix a compiler warning that status is defined by not used. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202512301641.FC6OAbGM-lkp@intel.com/ Signed-off-by: Mukesh R Signed-off-by: Wei Liu

x86/hyperv: Fix smp_ops build failure on UP kernels

2026-01-28T10:54:04Z

CI testing found this build failure: arch/x86/hyperv/hv_crash.c:631:9: error: ‘smp_ops’ undeclared (first use in this function) And I bisected it back to the initial commit that enabled this feature: 77c860d2dbb72d1f3c6a2e882a07d19eca399db5 is the first bad commit commit 77c860d2dbb72d1f3c6a2e882a07d19eca399db5 (HEAD) Author: Mukesh Rathor Date: Mon Oct 6 15:42:08 2025 -0700 x86/hyperv: Enable build of hypervisor crashdump collection files Hyperv should probably be limited to SMP kernels, as nobody appears to be testing it on UP kernels. Until then, fix the smp_ops assumption. Build tested only. Fixes: 77c860d2dbb72 ("x86/hyperv: Enable build of hypervisor crashdump collection files") Cc: Mukesh Rathor Cc: Wei Liu Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

x86/hyperv: Implement hypervisor RAM collection into vmcore

2025-11-15T06:18:16Z

Introduce a new file to implement collection of hypervisor RAM into the vmcore collected by linux. By default, the hypervisor RAM is locked, ie, protected via hw page table. Hyper-V implements a disable hypercall which essentially devirtualizes the system on the fly. This mechanism makes the hypervisor RAM accessible to linux. Because the hypervisor RAM is already mapped into linux address space (as reserved RAM), it is automatically collected into the vmcore without extra work. More details of the implementation are available in the file prologue. Signed-off-by: Mukesh Rathor Signed-off-by: Wei Liu