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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Oct 2025 16:53:12.4808 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fc8c7249-2012-478a-3817-08de17d4d029 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DB1PEPF000509F1.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS2PR08MB9497 Hi, > > > > > > > > Allow direct messages to be forwarded from the host. > > > > > > Signed-off-by: Sebastian Ene > > > Signed-off-by: Per Larsen > > > --- > > > arch/arm64/kvm/hyp/nvhe/ffa.c | 16 ++++++++++++++++ > > > 1 file changed, 16 insertions(+) > > > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c > > > index 4e16f9b96f637599873b16148c6e40cf1210aa3e..191dcb301cca3986758fb6a49f15f1799de9f1d1 100644 > > > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c > > > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c > > > @@ -857,6 +857,15 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res, > > > hyp_spin_unlock(&host_buffers.lock); > > > } > > > > > > +static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res, > > > + struct kvm_cpu_context *ctxt, > > > + u64 vm_handle) > > > +{ > > > + struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0]; > > > + > > > + arm_smccc_1_2_smc(args, res); > > > +} > > > + > > > > TBH, I don't have a strong comment for this but, I'm not sure why > > it is necessary. > > Since it calls just "smc" with the passed argments, > > I think it can be handled by default_smc_handler() without adding this > > function but return the ture for DIRECT MSG2 in ffa_call_support(). > > > > Am I missing something? > Calling `do_ffa_direct_msg` from the host ffa proxy ensures that the caller > has negotiated a FF-A version with the hypervisor first. In turn, > this means that `ffa_call_support` can use the negotiated version to decide > whether to proxy this interface or not. > > Moreover, `kvm_host_ffa_handler` currently proxies host FF-A calls. Android > also proxies FF-A calls from guest VMs via a similar function: > `kvm_guest_ffa_handler` so this function avoids duplication if/when adding a > guest proxy. This function is also where one would check FFA IDs before > forwarding messages (to prevent spoofing). You can see the downstream > implementation here > https://android-review.googlesource.com/c/kernel/common/+/3422040. Thanks for sharing and clarification. [...] Thanks. -- Sincerely, Yeoreum Yun