From: Russell King rmk+kernel@armlinux.org.uk
commit f5523423defb0d929e23813c8dd16c0131043a8c upstream.
Booting 5.4 on LX2160A reveals that KVM is non-functional:
kvm: Limiting the IPA size due to kernel Virtual Address limit kvm [1]: IPA Size Limit: 43bits kvm [1]: IDMAP intersecting with HYP VA, unable to continue kvm [1]: error initializing Hyp mode: -22
Debugging shows:
kvm [1]: IDMAP page: 81a26000 kvm [1]: HYP VA range: 0:22ffffffff
as RAM is located at:
80000000-fbdfffff : System RAM 2080000000-237fffffff : System RAM
Comparing this with the same kernel on Armada 8040 shows:
kvm: Limiting the IPA size due to kernel Virtual Address limit kvm [1]: IPA Size Limit: 43bits kvm [1]: IDMAP page: 2a26000 kvm [1]: HYP VA range: 4800000000:493fffffff ... kvm [1]: Hyp mode initialized successfully
which indicates that hyp_va_msb is set, and is always set to the opposite value of the idmap page to avoid the overlap. This does not happen with the LX2160A.
Further debugging shows vabits_actual = 39, kva_msb = 38 on LX2160A and kva_msb = 33 on Armada 8040. Looking at the bit layout of the HYP VA, there is still one bit available for hyp_va_msb. Set this bit appropriately. This allows KVM to be functional on the LX2160A, but without any HYP VA randomisation:
kvm: Limiting the IPA size due to kernel Virtual Address limit kvm [1]: IPA Size Limit: 43bits kvm [1]: IDMAP page: 81a24000 kvm [1]: HYP VA range: 4000000000:62ffffffff ... kvm [1]: Hyp mode initialized successfully
Fixes: ed57cac83e05 ("arm64: KVM: Introduce EL2 VA randomisation") Signed-off-by: Russell King rmk+kernel@armlinux.org.uk [maz: small additional cleanups, preserved case where the tag is legitimately 0 and we can just use the mask, Fixes tag] Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/E1ilAiY-0000MA-RG@rmk-PC.armlinux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kvm/va_layout.c | 56 ++++++++++++++++++++------------------------- 1 file changed, 25 insertions(+), 31 deletions(-)
--- a/arch/arm64/kvm/va_layout.c +++ b/arch/arm64/kvm/va_layout.c @@ -13,52 +13,46 @@ #include <asm/kvm_mmu.h>
/* - * The LSB of the random hyp VA tag or 0 if no randomization is used. + * The LSB of the HYP VA tag */ static u8 tag_lsb; /* - * The random hyp VA tag value with the region bit if hyp randomization is used + * The HYP VA tag value with the region bit */ static u64 tag_val; static u64 va_mask;
+/* + * We want to generate a hyp VA with the following format (with V == + * vabits_actual): + * + * 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0 + * --------------------------------------------------------- + * | 0000000 | hyp_va_msb | random tag | kern linear VA | + * |--------- tag_val -----------|----- va_mask ---| + * + * which does not conflict with the idmap regions. + */ __init void kvm_compute_layout(void) { phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start); u64 hyp_va_msb; - int kva_msb;
/* Where is my RAM region? */ hyp_va_msb = idmap_addr & BIT(vabits_actual - 1); hyp_va_msb ^= BIT(vabits_actual - 1);
- kva_msb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^ + tag_lsb = fls64((u64)phys_to_virt(memblock_start_of_DRAM()) ^ (u64)(high_memory - 1));
- if (kva_msb == (vabits_actual - 1)) { - /* - * No space in the address, let's compute the mask so - * that it covers (vabits_actual - 1) bits, and the region - * bit. The tag stays set to zero. - */ - va_mask = BIT(vabits_actual - 1) - 1; - va_mask |= hyp_va_msb; - } else { - /* - * We do have some free bits to insert a random tag. - * Hyp VAs are now created from kernel linear map VAs - * using the following formula (with V == vabits_actual): - * - * 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0 - * --------------------------------------------------------- - * | 0000000 | hyp_va_msb | random tag | kern linear VA | - */ - tag_lsb = kva_msb; - va_mask = GENMASK_ULL(tag_lsb - 1, 0); - tag_val = get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb); - tag_val |= hyp_va_msb; - tag_val >>= tag_lsb; + va_mask = GENMASK_ULL(tag_lsb - 1, 0); + tag_val = hyp_va_msb; + + if (tag_lsb != (vabits_actual - 1)) { + /* We have some free bits to insert a random tag. */ + tag_val |= get_random_long() & GENMASK_ULL(vabits_actual - 2, tag_lsb); } + tag_val >>= tag_lsb; }
static u32 compute_instruction(int n, u32 rd, u32 rn) @@ -117,11 +111,11 @@ void __init kvm_update_va_mask(struct al * VHE doesn't need any address translation, let's NOP * everything. * - * Alternatively, if we don't have any spare bits in - * the address, NOP everything after masking that - * kernel VA. + * Alternatively, if the tag is zero (because the layout + * dictates it and we don't have any spare bits in the + * address), NOP everything after masking the kernel VA. */ - if (has_vhe() || (!tag_lsb && i > 0)) { + if (has_vhe() || (!tag_val && i > 0)) { updptr[i] = cpu_to_le32(aarch64_insn_gen_nop()); continue; }