On Sun, Feb 07, 2021 at 08:01:50AM -0800, Dave Hansen wrote: > On 2/7/21 6:13 AM, Kirill A. Shutemov wrote: > >>> + /* Allow to pass R10, R11, R12, R13, R14 and R15 down to the VMM > >>> */ > >>> + rcx = BIT(10) | BIT(11) | BIT(12) | BIT(13) | BIT(14) | BIT(15); > >>> + > >>> + asm volatile(TDCALL > >>> + : "=a"(ret), "=r"(r10), "=r"(r11), "=r"(r12), > >>> "=r"(r13), > >>> + "=r"(r14), "=r"(r15) > >>> + : "a"(TDVMCALL), "r"(rcx), "r"(r10), "r"(r11), > >>> "r"(r12), > >>> + "r"(r13) > >>> + : ); > >> Some "+" constraints would make this simpler. But I think you should > >> factor the TDCALL helper out into its own function. > > Factor out TDCALL into a helper is tricky: different TDCALLs have > > different list of registers passed to VMM. > > Couldn't you just have one big helper that takes *all* the registers > that get used in any TDVMCALL and sets all the rcx bits? The users > could just pass 0's for the things they don't use. > > Then you've got the ugly inline asm in one place. It also makes it > harder to screw up the 'rcx' mask and end up passing registers you > didn't want into a malicious VMM.
For now we only pass down R10-R15, but the interface allows to pass down much wider set of registers, including XMM. How far do we want to get it? -- Kirill A. Shutemov
