[PATCH 4/5] UBUNTU: SAUCE: Drivers: hv: vmbus: support >64 VPs for a TDX VM without the pavavisor
Tim Gardner
tim.gardner at canonical.com
Mon Jul 24 17:00:16 UTC 2023
From: Dexuan Cui <decui at microsoft.com>
BugLink: https://bugs.launchpad.net/bugs/2028286
Don't set *this_cpu_ptr(hyperv_pcpu_input_arg) before the call
set_memory_decrypted() returns, otherwise we can run into this ticky issue:
1. In hv_common_cpu_init(), *this_cpu_ptr(hyperv_pcpu_input_arg) is set to
a private (i.e. encrypted) page.
2. hv_common_cpu_init() -> set_memory_decrypted() -> __set_memory_enc_dec ->
__set_memory_enc_pgtable() -> cpa_flush() -> on_each_cpu() ->
on_each_cpu_cond_mask() -> smp_call_function_many_cond() ->
arch_send_call_function_ipi_mask() -> smp_ops.send_call_func_ipi() ->
native_send_call_func_ipi() -> apic->send_IPI_allbutself() ->
hv_send_ipi_allbutself() -> hv_send_ipi_mask_allbutself() ->
__send_ipi_mask():
When the VM has >64 vCPUs, __send_ipi_mask_ex() is called:
arg = (struct hv_send_ipi_ex **)this_cpu_ptr(hyperv_pcpu_input_arg);
ipi_arg = *arg;
hv_do_rep_hypercall(HVCALL_SEND_IPI_EX, 0, nr_bank, ipi_arg, NULL);
The hv_do_rep_hypercall() will trigger a fatal fault because Hyper-V
requires that the 'ipi_arg' should point to a shared (i.e. decrypted) page.
Avoid the fatal fault by setting *this_cpu_ptr(hyperv_pcpu_input_arg) after
calling set_memory_decrypted() returns: by doing this, __send_ipi_mask_ex()
returns HV_STATUS_INVALID_PARAMETER because *this_cpu_ptr(hyperv_pcpu_input_arg)
is still NULL, and __send_ipi_mask() returns false, meaning hv_send_ipi_allbutself()
calls orig_apic.send_IPI_all(), i.e. x2apic_send_IPI_all), to send IPIs.
x2apic_send_IPI_all() doesn't depend on *this_cpu_ptr(hyperv_pcpu_input_arg.
Signed-off-by: Dexuan Cui <decui at microsoft.com>
(cherry picked from commit f1e61e384cae06a16b97c63fa2238313ad090a3c https://github.com/dcui/linux)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
drivers/hv/hv_common.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 6c1fcfc6894a..23871a9d02e9 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -129,6 +129,7 @@ int hv_common_cpu_init(unsigned int cpu)
u64 msr_vp_index;
gfp_t flags;
int pgcount = hv_root_partition ? 2 : 1;
+ void *mem;
int ret;
/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
@@ -141,25 +142,26 @@ int hv_common_cpu_init(unsigned int cpu)
* allocated if this CPU was previously online and then taken offline
*/
if (!*inputarg) {
- *inputarg = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
- if (!(*inputarg))
+ mem = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);
+ if (!mem)
return -ENOMEM;
if (hv_isolation_type_tdx()) {
- ret = set_memory_decrypted((unsigned long)*inputarg, pgcount);
- if (ret) {
- /* It may be unsafe to free *inputarg */
- *inputarg = NULL;
+ ret = set_memory_decrypted((unsigned long)mem, pgcount);
+
+ /* It may be unsafe to free mem upon error. */
+ if (ret)
return ret;
- }
- memset(*inputarg, 0x00, pgcount * HV_HYP_PAGE_SIZE);
+ memset(mem, 0x00, pgcount * HV_HYP_PAGE_SIZE);
}
if (hv_root_partition) {
outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
- *outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
+ *outputarg = (char *)mem + HV_HYP_PAGE_SIZE;
}
+
+ *inputarg = mem;
}
msr_vp_index = hv_get_register(HV_REGISTER_VP_INDEX);
--
2.34.1
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