From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical. Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/alpha/lib/strchr.S | 72 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 arch/alpha/lib/strchr.S (limited to 'arch/alpha/lib/strchr.S') diff --git a/arch/alpha/lib/strchr.S b/arch/alpha/lib/strchr.S new file mode 100644 index 000000000..68c54ff50 --- /dev/null +++ b/arch/alpha/lib/strchr.S @@ -0,0 +1,72 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * arch/alpha/lib/strchr.S + * Contributed by Richard Henderson (rth@tamu.edu) + * + * Return the address of a given character within a null-terminated + * string, or null if it is not found. + */ +#include +#include + + .set noreorder + .set noat + + .align 3 + .globl strchr + .ent strchr +strchr: + .frame sp, 0, ra + .prologue 0 + + zapnot a1, 1, a1 # e0 : zero extend the search character + ldq_u t0, 0(a0) # .. e1 : load first quadword + sll a1, 8, t5 # e0 : replicate the search character + andnot a0, 7, v0 # .. e1 : align our loop pointer + or t5, a1, a1 # e0 : + lda t4, -1 # .. e1 : build garbage mask + sll a1, 16, t5 # e0 : + cmpbge zero, t0, t2 # .. e1 : bits set iff byte == zero + mskqh t4, a0, t4 # e0 : + or t5, a1, a1 # .. e1 : + sll a1, 32, t5 # e0 : + cmpbge zero, t4, t4 # .. e1 : bits set iff byte is garbage + or t5, a1, a1 # e0 : + xor t0, a1, t1 # .. e1 : make bytes == c zero + cmpbge zero, t1, t3 # e0 : bits set iff byte == c + or t2, t3, t0 # e1 : bits set iff char match or zero match + andnot t0, t4, t0 # e0 : clear garbage bits + bne t0, $found # .. e1 (zdb) + +$loop: ldq t0, 8(v0) # e0 : + addq v0, 8, v0 # .. e1 : + nop # e0 : + xor t0, a1, t1 # .. e1 (ev5 data stall) + cmpbge zero, t0, t2 # e0 : bits set iff byte == 0 + cmpbge zero, t1, t3 # .. e1 : bits set iff byte == c + or t2, t3, t0 # e0 : + beq t0, $loop # .. e1 (zdb) + +$found: negq t0, t1 # e0 : clear all but least set bit + and t0, t1, t0 # e1 (stall) + + and t0, t3, t1 # e0 : bit set iff byte was the char + beq t1, $retnull # .. e1 (zdb) + + and t0, 0xf0, t2 # e0 : binary search for that set bit + and t0, 0xcc, t3 # .. e1 : + and t0, 0xaa, t4 # e0 : + cmovne t2, 4, t2 # .. e1 : + cmovne t3, 2, t3 # e0 : + cmovne t4, 1, t4 # .. e1 : + addq t2, t3, t2 # e0 : + addq v0, t4, v0 # .. e1 : + addq v0, t2, v0 # e0 : + ret # .. e1 : + +$retnull: + mov zero, v0 # e0 : + ret # .. e1 : + + .end strchr + EXPORT_SYMBOL(strchr) -- cgit v1.3.1